Vlan traffic issue

[Mr. Andrew]

We have a collapsed core network, with some 4500s as our core node layer. I changed the Data and Voice VLAN IDs around to be the same across our network along with their SVIs. However, we have one switch that connects to two core nodes. one of the 4500s connects to our DHCP server and computer and phone dhcp traffic is going through their respective default gateway to the redundant access switch to the other 4500 and pulling an IP from that SVI. 

Attached is a simple drawing of whats going on to better understand. VOIP traffic is taking the red route instead of the intended blue route. Causing some devices to pull from a different subnet. Helper addresses are configured on the CNs. I would just like to prevent DHCP broadcast frames from reaching the other CN. 

 

[balaji.bandi]

can you post some config, and routing information, how did you come to conclusion that traffic traversing via access node ?

[Mr. Andrew]

Some phones and PCs had their default gateway set as the other core node. I also did a sh mac add on the redundant access switch and saw a lot of MACs were traversing the trunks that shouldn’t be. 

[balaji.bandi]

If this later 2 network, and access switch acting as root bridge for VLAN, then if that is only i see reason.

still i insists to see your routing and config information for us to undersand the issue and advise correctly.

[MHM Cisco World]

the VoIP and DHCP share same subnet that way the traffic is bridge not routing in first 4500 (that VoIP connect to)
you need to config 
different VLAN for DHCP
config IP helper in 4500 

[frknl]

posting, configs and named topology diagram could be more helpful.

[paul driver]

Hello
Are you manaully prunning on the trunk interconnects, or would it be feesible to do do?

[Mr. Andrew]

My fix action was too manually prune the data and voice vlan on one of the access switches trunk interfaces, but it kills the redundancy idea for that access node. Im just curious if there is a way to block the layer 2 dhcp frames from going through the redundant access node and using the routed interface via the helper address.

[paul driver]

Hello

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@Mr. Andrew wrote:

Im just curious if there is a way to block the layer 2 dhcp frames from going through the redundant access node and using the routed interface via the helper address.

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You could but then again your resilency would be broken

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@Mr. Andrew wrote:

VOIP traffic is taking the red route instead of the intended blue route. Causing some devices to pull from a different subnet

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This is something i am not sure about, why are some of your voip devices obtaining an address from another subnet unless you have the dhcp scopes appended to the wrong vlans or you have overlapping native vlans

[Georg Pauwen]

Hello,

post the fulll running configs of all devices, and put a description on the connecting ports so we can see how everything is linked.